Certification Examination Practice

Illinois Soils and Aggregate Technician Certification Examination Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following is the primary purpose of conducting a sieve

analysis on aggregate?

• To measure chemical composition
• To determine particle size distribution
• To assess mineralogy
• To determine color

Rationale: Sieve analysis is used to determine the particle size

distribution (gradation) of an aggregate sample, which affects strength, workability, and compaction.

• What does the term "fines" generally refer to in aggregate testing?
• Particles retained on the 3/8-inch sieve 1 / 4

• Particles passing the No. 200 sieve (0.075 mm)
• Particles between 1 mm and 4.75 mm
• Coarse particles larger than 4.75 mm

Rationale: In common practice, "fines" are the very small particles

that pass the No. 200 sieve (0.075 mm) and influence plasticity and water demand.

• Which test determines the water content at which a soil changes from

a plastic to a liquid state?

• Compactibility test
• Shrinkage limit test
• Liquid limit test (Atterberg liquid limit)
• Specific gravity test

Rationale: The liquid limit is the water content at which a soil passes

from the plastic state to the liquid state and is assessed by standardized Atterberg procedures.

4. The Plasticity Index (PI) is defined as:

• Liquid limit × Plastic limit
• Liquid limit + Plastic limit
• Liquid limit − Plastic limit
• Plastic limit − Liquid limit

Rationale: PI measures the range of water content where the soil is

plastic; it is the difference between liquid limit and plastic limit. 2 / 4

• In the Standard Proctor test, what is being determined?
• Soil chemical reactivity
• Maximum dry density and optimum moisture content
• Gradation of aggregate
• Permeability of soil

Rationale: The Standard Proctor test determines the compaction

characteristics—maximum dry density and the moisture content at which it occurs (optimum moisture).

• A coarse aggregate sample’s specific gravity is required for mix design.

Specific gravity is the ratio of:

• Mass of dry sample to mass of water it displaces
• Mass of a unit volume of aggregate to mass of an equal volume of

water

• Volume of aggregate to volume of voids
• Bulk density to void ratio

Rationale: Specific gravity compares the mass of a given volume of

material to that of the same volume of water; it is needed for volumetric calculations.

• Which sieve size is commonly used as the boundary between coarse

and fine aggregate in many standards?

• No. 10 sieve (2.00 mm)
• No. 4 sieve (4.75 mm)
• No. 40 sieve (0.425 mm) 3 / 4

• 3/8-inch sieve (9.5 mm)

Rationale: The No. 4 sieve (4.75 mm) is commonly used as the

dividing line between fine and coarse aggregates in many specifications.

• What does absorption percentage of aggregate describe?
• Percentage of fines present
• Amount of water absorbed by aggregate (by mass) when fully

saturated

• Volume of voids in aggregate mass
• Loss after abrasion testing

Rationale: Absorption is the water uptake by aggregate particles

when saturated, expressed as a percentage of dry mass, affecting mix water demand.

• Which procedure is used to determine the clay fraction of a soil

sample that affects plasticity?

• Sieve analysis only
• Hydrometer analysis
• Specific gravity test
• Proctor compaction

Rationale: Hydrometer analysis measures the distribution of fine

particles (silt and clay) by sedimentation, identifying the clay fraction important for plasticity.

• / 4